The invention relates to the efficient and cost-effective recovery of component materials from an unsorted or contaminated feedstock. The invention is especially useful for recovering polymeric material by removing metal debris from polymer fiber feedstocks, such as from textile wastes.
Textile manufacturers and suppliers are continually challenged by the generation of textile waste, such as waste carpet. Each year, large quantities of textile wastes are simply landfilled. Disposing of textile wastes in this way is not only expensive, but also runs counter to increasing corporate emphasis on environmental stewardship. In short, merely discarding textile wastes precludes the recovery of useful component materials.
The presence of tramp metal debris in textile wastes complicates recycling efforts. Coarse metal debris can damage recycling equipment and so must be removed. This reduces recycling efficiency, frequently rendering recovery of the desired components too costly to be practical.
Current processes for recovering textile waste components often require complicated and expensive integration of numerous unit operations, and yet achieve modest results. For example, typical processes employ magnets to remove tramp metal debris from textile wastes. In some processes, this requires frequent process stoppages so that metal debris can be removed by hand. In other processes, the magnets have auto-clean mechanisms, but this often compromises performance.
In addition, magnets effectively capture only ferrous metals. Thus, some metal detectors employ integrated debris rejection devices that work on non-ferrous metal. Such detector-rejection devices, however, are not only expensive, but also complicated—establishing and maintaining a target sensitivity is difficult. Moreover, because recyclable materials (i.e., polymer fibers) become carryover losses with each detection-rejection sequence, the size threshold that triggers detection must be set to limit product yield loss.
A need continues to exist for an efficient and cost-effective system for separating and recovering the components of polymer fiber wastes such that the recovered materials are sufficiently uncontaminated to facilitate immediate recycling. In particular, there is a need for a system to remove metal debris from all kinds of textile wastes, including waste carpet.